The present invention relates to a state control system in a recording equipment or apparatus incorporating a distributed CPU system.
In such a recording equipment as a copying machine, it has been in practice to employ a distributed CPU system, in which the entire system is divided into a plurality of subsystems, which individually perform their respectively required processes, and a main system performs an overall coordinating control over the operations of such subsystem, thereby integrating them into an organically structured system. In this system, a user interface (U/I), for example, constantly monitors the condition of keys. When the user enters any input with operations on the keys, the U/I judges what job mode has been input, and transmit a signal to the main system. Upon the reception of such a signal, the main system issues instructions to the individual subsystems to make preparations. Then, in response, the subsystems give a command indicating the completion of preparations, and the main system verifies the completion of the preparations by the system as a whole and thereafter gives a command for the execution of the job to the individual subsystems.
In order to perform the processes mentioned above in an unfailing and smooth way, it has also been in practice until the present time to divide the operating sequence into several states and to specify beforehand the processes which the individual subsystems should perform in each state, with such states being controlled by the main system. That is to say, the main system rewrites the state when the process to be executed in a given state has been completed and monitors the status of execution of the process to be performed in the next state. The control of the states in this manner has simplified the overall control of all the subsystems with an effective grasp of the status of the individual subsystems, thereby achieving efficient control over an expanding system and also accomplishing greater accuracy and a higher speed in the execution of the processes by the system as a whole in such a way that this system setup provides adequate means and measures for dealing with the multiple functions incorporated into recording machines or the like and with the higher operating speed of such machines.
Now, the conventional distributed CPU system offers the merit that it can operate with a fewer number of intermodular interfaces since it uses a small number of modules to perform the job control and to give instructions to the individual subsystems as the U/I performs the job control, such as the monitoring of the operations on the keys, the types and substance of the jobs input into the system, and the presence or absence of any contradiction of the job demanded by the input, while the main system issues instructions to the individual subsystems on the basis of the job mode which is transmitted from the U/I and gives execution commands to the individual systems on the basis of the responses from them. Yet, such a system presents the problem that the processing operations are concentrated on the U/I and the main system, with the result that the modules which perform such operations grow considerably large. In addition, the existing system is also faced with the problem that it can not be modified readily because alterations of the specifications require complicated work as an addition, change, or reduction of a given subsystem is necessarily accompanied with modifications of the main system, which gives instructions to the individual subsystems since the main system performs overall control of the entire system. Therefore, it is difficult to improve the productivity of the software, to detect bugs in it and to correct them, and such difficulties present problems from the viewpoint of the manufacturing processes.
The present invention has been made in order to overcome the problems mentioned above.